A hot December made cooler with Powerwall 2’s

Tesla Powerwall 2's mounted

I was a relatively early adopter of a Tesla Powerwall 2, I had my first Powerwall installed on October 31st 2017. It was a relatively simple exercise via Solaray Energy who installed most of my existing Enphase solar array. (I’ll cover solar in a separate, future blog post)

After going through the 2017 summer period, I pretty quickly realised that a single Powerwall 2 just wasn’t cutting it, especially when I had thoughts of a Model 3 reservation, so in late January 2018 I placed an order for another Powerwall 2 plus the expansion of my existing solar array by another 3kW.

Two wall mounted Tesla Powerwall 2’s with home backup gateway and Enphase Envoy enclosure

Two Powerwall 2’s will provide approximately 27kWh of energy to use when there isn’t sufficient solar generation to meet house consumption. Two Powerwall 2’s will also supply power up to 10kW constant with the ability to burst to 14kW.

Powerwalls getting some serious energy from the sun!

Down here in the southern hemisphere, December is one of the hottest months of the year. I’m terrible when it comes to tolerating heat so our ducted air-conditioning gets a lot of use!

Averaging just over 27kWh of usage per day in December 2018
Power usage generally increased week on week during December 2018

So, if we were to break this down in terms of costs for the month without Solar or Powerwall storage, we’d end up with:

  • Daily Supply Charge – $0.924 per day * 31 = $28.64
  • Power Usage (From grid) – $0.3179 per kWh * 849 = $269.90
  • Total bill = $298.54 – for a single month of power!

Enter Solar and Powerwall 2!

Lets take a look at these figures now taking into account both Solar and Powerwalls running:

  • Daily Supply Charge – $0.924 per day * 31 = $28.64
  • Power Usage (from grid) – $0.3179 per kWh * 5.5 = $1.75
  • Solar Credits (to grid) – $0.20 per kWh * 586 – ($117.20)
  • Total bill = ($86.81) – that’s a little better!

That equals a total saving of $385.35 for the month of December alone! It will be interesting to see what the January statistics bring!


Author: Adam

2 thoughts on “A hot December made cooler with Powerwall 2’s

  1. Hi Adam,

    Interesting to see what other Powerwall 2 owners are doing.

    Just a correction:-
    Power is measured in watts (W) or kilowatts (kW).
    Electrical energy is measured in watthours (Wh) or kiloWatthours (kWh).

    Power is work being performed instantly.
    Energy is power over time.

    So, for your system, you have 27kWh of energy storage being able to be delivered up to 10kW continuously (or 14kW for short burst of peak power). (A bit envious there).

    I’ve had my Powerwall just over 12 months now. 99% of the time it has worked well. There’s been about 3 occasions where I had to reset the PW to get it going. Don’t know why it locked up.

    Otherwise, keep up the good updates.


    1. Thanks so much for reading my blog Graham!

      I appreciate the clarifications on kW versus kWh, I’ll make some edits to this post based on your feedback!

      Have a great day!


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